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From "Shalin Shekhar Mangar (JIRA)" <j...@apache.org>
Subject [jira] [Created] (SOLR-6524) Collections left in recovery state after node restart because recovery sleep time increases exponentially between retries
Date Tue, 16 Sep 2014 13:15:34 GMT
Shalin Shekhar Mangar created SOLR-6524:
-------------------------------------------

             Summary: Collections left in recovery state after node restart because recovery
sleep time increases exponentially between retries
                 Key: SOLR-6524
                 URL: https://issues.apache.org/jira/browse/SOLR-6524
             Project: Solr
          Issue Type: Bug
          Components: SolrCloud
            Reporter: Shalin Shekhar Mangar
             Fix For: 4.11


The RecoveryStrategy has a retry wait which is exponential in nature. The first time it waits
for 1 second before retrying recovery, then 2 seconds, then 4 seconds and so on.

This causes problems when running a large number of collections in SolrCloud. We saw a case
where there were 500 collections on 3 nodes (1 shard, 3 replicas) and after a node is restarted,
many collections can't come back up from recovery because:
# The overseer is slow to process events (I'll create another issue for it)
# Because the overseer is slow, cluster state updates are delayed and therefore recovery cannot
succeed (WaitForState hangs while waiting to see recovery state on replicas)
# Because recovery can't succeed immediately, the recovery thread sleeps for larger and larger
amounts of time
# Even after the whole overseer queue is cleared up, many recovery threads have such a long
sleep that they won't even attempt to recover for many minutes (upto 10 minutes).



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